A ski is described in EP 1 484 091 B1 (Salomon S. A.), by which the radius of trajectory by running on the left ski edge differs from the radius of trajectory by running on the right ski edge. Such ski comprising a core, below which a bottom set of bearing layers is arranged, below which a sliding surface is available together with ski edges, and above said core there is a top set of bearing layers, above which appropriately decorated top covering layer is placed. The core and the top set of bearing layers are specially designed such that said set of bearing layers is inclined downwards along at least one lateral surface of the ski towards the corresponding ski edge. At least one layer of said set of layers is designed asymmetric, by which the ski is locally reinforced in a desired area on the one side of the longitudinal axis of the ski, so that its bending and/or torsion rigidity in said area is then higher than on the opposite side of said longitudinal axis. As known, a pair of skis is usually used. When by manufacturing of each pair of skis the same core is used in both skis, upon which several asymmetric layers are placed above such core, this should then lead to asymmetric visual appearance of the shape of such ski. Characteristics of such skis like bending and torsion stiffness in the area of the left and right ski edge, are then also asymmetric, in particular when asymmetric core is used by manufacturing of such ski, wherein also the visual appearance of such ski is quite obviously asymmetric. However, by means of just providing said asymmetric bearing layers it is impossible to assure that during regular turning such skis left or right, the running trajectories of both skis in each pair along the left or right ski edges would be at least essentially equidistant.
Furthermore, a ski is described in EP 0 661 086 (Skis Rossignol S. A.), which comprises a core, a bottom bearing layer located below said core and a top bearing layer located above the core. A sliding surface with ski edges is located below said bottom bearing layer, and the top covering layer is located above the top bearing layer. Said core is laterally covered by side walls. Said core is furnished with a strip, which in the area of the front portion and the rear portion of the ski extends parallel to said top bearing layer and bottom bearing layer, while in the central portion of the ski said strip is deflected i.e. inclined with respect to said top bearing layer and bottom bearing layer. Consequently, by loading such ski during the use, asymmetric bending and torsion deformations should be expected along both ski edges. In general, such approach should not lead to asymmetric visual appearance of the ski. It must however be taken into consideration that just slight deflection of said strip at e.g. several degrees of inclination cannot result in essential difference between the radius of the trajectory by turning such ski left or right. By increasing said inclination of the strip in the central portion of the ski, thickness of the core is essentially increased and consequently also the overall thickness of the ski in the central portion thereof, which results in elevation of the standing position and moreover also to essential increasing of stiffness and reduction of elasticity of the ski in the central portion thereof. Moreover, thanks to the shape of said strip, the front portion and the rear portion of the ski would theoretically have to be rotated relatively to the central portion of the ski as soon as the ski is exposed to compression and bending of the central region thereof. This on the one hand means that by running the ski straightforward, by bending the ski exclusively in the vertical direction, such ski automatically exposes tendency of turning and running out from said straightforward direction. On the other hand, when turning, the external ski of each pair of skis is usually exposed to much extensive loadings than the internal ski, which means that more extensive rotation of the front portion and the rear portion of the external ski results in running the ski along the trajectory with smaller radius, by which the external ski is rapidly approaching to the internal ski, which can be then corrected by means of appropriate sideslip of at least one ski edge, which leads to essential decrease of velocity and much more difficult control of the ski by turning.
Still further, CH 681 061 A5 (Haldemann) discloses a ski, which also comprises a core, a bottom bearing layer located below said core, ad a top bearing layer located above said core. A sliding surface with ski edges is located below said bottom bearing layer, and the top covering layer is located above the top bearing layer. Said core is laterally covered by side walls. For the purposes of increasing torsion rigidity of each ski in each pair of skis, a supplemental bearing layer is placed above the top bearing layer and extends asymmetrically with regard to the central longitudinal axis of each ski. When observing the left ski, said supplemental layer is placed over the central portion of the ski along the complete width, while on the front portion and the rear portion of the ski said supplemental layer is available exclusively above the region of the right ski edge. On the contrary, on the left ski, said supplemental layer is placed over the central portion of the ski along the complete width, while on the front portion and the rear portion of the ski said supplemental layer is available exclusively above the region of the left ski edge. Such measure results in increased torsion rigidity in the region of that ski edge, which is by turning the ski left or right more exposed to torsional deformations, which in particular by running the skis along the compact iced ground lead to sideslip of the loaded ski edge in combination with vibrations and similar undesired effects. Again, furnishing the ski with said supplemental layer, which is capable to essentially improve characteristics of the ski. leads to essential increasing of the thickness of the ski, and consequently also of its weight and bending rigidity. Those skilled in the art will understand, that also in this case such asymmetric concept unavoidable leads to amended visual appearance of the ski and asymmetric shape of the ski as such. It is also clear that just increasing of the torsion rigidity of the external ski in each pair of turning skis cannot contribute in the sense of reliable running of the external and the internal ski on approximately unchangeable distance apart from each other, since the above mentioned measures rather result in completely opposite effect.
A ski with asymmetric characteristics is disclosed in EP 2 248 560 A1 (Zai A G). The front and rear portion of such ski are torsionally bent around the longitudinal axis relative to the central portion, which results in various radius of curvature of the left and right ski edge when ski is loaded i.e. compressed with a pre-determined certain force. Such ski has not only asymmetric characteristics but also apparently asymmetric appearance, and is quite difficulty maintained in each desired direction along straightforwards sections of the skiing trajectory.
A further ski with asymmetric characteristics is disclosed in FR 2 659 562 A1 (Rossognol S A). Said asymmetric characteristic is achieved by means of removing a part of the front and rear portion of the ski, wherein the missing portions are then replaced with a non-bearing part, e.g. a plastic insert or the like, by which the appearance of an usual ski with a complete and symmetric silhouette shall be assured. Such ski has asymmetric characteristics but visually differs from ordinary skis. Besides, said non-bearing parts must be manufactured separately and in addition to other components of a ski, wherein also such modified ski must be further specially adapted for firmly and reliable attachment of said additional parts, in particular, since the ski as a whole is usually exposed to essential impacts and vibrations during the practical use.